Insertion-type earphone devices that are used in a state in which a part is inserted into the outer ear canal of the user have come into widespread use in recent years (see Patent Literature 1 and 2, for example). This type of earphone device has a sound generator that generates sound by receiving the input of electrical signals, a case main body that houses the sound generator, a sound conduit that sticks out from the case main body, and an ear tip. The ear tip is formed from a resilient material (such as soft rubber) and can be attached to the sound conduit. When the user uses the earphone device, the ear tip is attached to the sound conduit, and the sound conduit is inserted into the outer ear canal of the user in a state of being covered by the ear tip. Sound generated by the sound generator is transmitted through a hole formed in the sound conduit, and is emitted from the distal end of the ear tip of the earphone device.
With the earphone devices disclosed in Patent Literature 1 and 2, the ear tip is fixed to the sound conduit by being fitted into the sound conduit.
The insertion type of earphone device discussed above is used in a state in which the ear tip is disposed so as to block off the outer ear canal of the user. This reduces the effect of external noise and helps to improve sound quality. The ear tip also functions as a cushioning member, which prevents the sound conduit from coming into contact with the outer ear canal of the user.
Meanwhile, there is also a known earphone device that takes into account the great variety of shapes and sizes in the outer ear canal of users. For instance, a plurality of ear tips of different size and design may be provided as accessory parts to an earphone device so that the user can replace the ear tip to match personal preference or the size of the outer ear canal.    Patent Literature 1: Japanese Laid-Open Patent Application 2005-191663    Patent Literature 2: Japanese Laid-Open Patent Application 2007-189468